Computing power becomes a needed resource just like electricity and water supply that are essential resources for civilization. Computing power is necessary to process the ever increasing business data, engineering and scientific problems, to enhance digital multimedia and entertainment experience and in many other aspects that affect most people's life. Since computers were first introduced, the need for computational power is progressively increasing. Computer vendors are challenged by the ever increasing computing power demand. Every year new software applications are being released and typically requiring more computing resources. Every year computer vendors must upgrade their product offerings to provide better performance, more graphic power, and more memory and storage. To remain competitive in this ever changing market vendors must continuously adopt the fastest and higher density processors and chipsets. The demand for faster computing power pushes the computing supply-chain toward higher performance, larger capacities, and lower pricing. These trends are even more significant in the server industry as more powerful servers are needed for IT organizations to satisfy the ever increasing demand for computational power and data handling in their organizations.
Current technology computers and servers are characterized by low density compared to pure silicon mass and volume. As silicon is the platform “payload”—where computation and memory is taking place, the rest of the computer can be considered as “overheads” such as interconnects, cooling, enclosures, and power functions. This low density results from 2-D structure that is based on Printed Circuit Boards (PCBs) forming the motherboard. In a typical desktop only less than 1% of the volume and the mass of the computer is the silicon payload, the other 99% are overheads. Inefficiencies result from the 2-D nature of the chip interconnections, PCBs, and other connectors and wiring. Some perpendicular boards can improve the device density, but still both the volumetric efficiency and mass efficiency are typically low.
One option known in the prior art is the blade server—a combination of a rack that can host several parallel modules (blades) and a perpendicular backplane that interconnects these blades to one or more management modules, power supplies, and network switches. While this option tends to increase the device volumetric and mass efficiency, it suffers from cooling problems, standardization problems, and higher costs. The air-flow necessary to dissipate the heat generated at the blade chips and power components requires wide flow paths and generates strong acoustic noise. Another disadvantage of the current technology blade servers is the lack of standardization at any level. Chips, boards, and modules are not interchangeable between vendors or between different models of the same vendor. As density of blade servers increases so the heat dissipation problem increases. With increased components density there is a need to pass faster air while air-paths become smaller. This tends to challenge the modules and rack design and dramatically affect the system performance and reliability.
One area where volumetric efficiency is critical is in the data-centers. Data-centers are characterized by high cost per rack vertical space. Any increase in the performance or capacity per rack space can be immediately translated into cost savings. Organizations that operate large numbers of server cores at their data-centers are always seeking technologies that enable them to get more performance per U (vertical standard equivalent to 1.75 inches/44.5 mm) in their racks.
The rapid development of interconnect bus technologies, memory technologies, CPU technologies and storage reduces the capability to standardize components between platforms. As a result of that platforms that were the best technology just three years ago may become non-standard and obsolete today. A large amount of computer equipment is dumped as waste every year, and this becomes one of the most problematic types of environmental waste. Computer equipment contains many polluting and hazardous materials, and the short life cycle of this equipment generates a huge amount of waste materials. Increasing the life cycle of computing equipment together with reduction of volume and mass can dramatically reduce computer related wastes and therefore will be environmentally safer. New rules and regulations about waste electronics equipment were enacted to reduce pollution and waste. Electronic related products had becomes a global pollution source, and any innovation that reduces its volume will be embraced by the European community and many other governments).
Another major disadvantage of the current technology 2-D computers and servers is the signal trace length. To bridge between the different components located on the motherboard, longer PCB traces are needed. The design around longer traces limit the bus speeds, causes larger latencies, causes cross-talk between signals, increases the noise pickup, worsens the signal shape due to parasitic capacitance and parasitic inductance, and causes electromagnetic noise that may affect other devices nearby.
Another design problem with the current 2-D computers and servers is the low density interconnects. The need to include in the design the options to connect additional modules or components on the mother board requires designs to include many used or unused low density connectors. As these connectors are built for PCB modules, the maximum pitch possible is around 0.5 mm at each side. With today's 64 and 128 bit busses, this results a long connector. The problem becomes even more severe if the connector stays unused. In this case many fast signals may stay exposed without proper terminations.
Another option to build higher performance and higher density computers known in the prior art is Massively Parallel Processing (MPP) systems. Computing systems comprised of hundreds or thousands of Processing Elements (PEs) individually interconnected by a common high-speed communication network. The arrangement of PEs in 3-D array structures enables better connectivity between PEs and therefore yield higher performance in these demanding applications. A typical example is Cray XT3 parallel processing supercomputer that relies on AMD Opteron commercial 64 bit processor and Cray's SeaStar 3-D interconnect technology. While this architecture offers higher density and 3-D cores connectivity scheme, it still suffers from high costs and limited density improvement compared to traditional servers. This current technology MPP is typically built as 3-D mesh structures at the motherboards level, and still each core being used as PE is 2-D structure with traditional PCBs structure. These design challenges described above and many other inherent problems typical for the current 2-D computer design methodology yield limited busses and interconnect performance and as a result-limited system overall performance and lower reliability.